Carmen Rosales | Universidad Simón Bolívar (original) (raw)
Papers by Carmen Rosales
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, Dec 1, 2017
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, 2017
La acumulacion de virutas de polietileno de ultra alto peso molecular (PEUAPM), producto del meca... more La acumulacion de virutas de polietileno de ultra alto peso molecular (PEUAPM), producto del mecanizado de elementos de maquina, genera diversos problemas en las plantas de produccion. Con el objeto de plantear una posible reutilizacion de estos residuos y reducir su impacto sobre el ambiente, se prepararon mezclas con base en diferentes proporciones de este material y dos polietilenos de alta densidad (PEAD): grado extrusion y grado inyeccion. Se evaluaron las propiedades reologicas y mecanicas (traccion y abrasion) de las mezclas preparadas y se observo su morfologia mediante microscopia electronica de barrido. Todas las mezclas fueron procesadas en una extrusora de doble tornillo y se moldearon placas por compresion. Cuando se compararon los diferentes productos con los PEAD puros, todos exhibieron un aumento en la resistencia a la abrasion, se obtuvieron pocas variaciones en las propiedades en traccion y se encontro un aumento de las viscosidades complejas y de los modulos de almacenamiento y de perdidas con el contenido de PEUAPM. Ademas, es de resaltar que se logro preparar un nuevo material (PEAD grado inyeccion/PEUAPM, 80/20) con propiedades de traccion y comportamiento reologico semejantes al PEAD grado extrusion, que podria sustituir a este ultimo en aplicaciones similares
In the present work, the influence of the degradation during the processing of nanocomposites of ... more In the present work, the influence of the degradation during the processing of nanocomposites of poly (lactic acid) (PLA) with montmorillonite and its blends with low density polyethylene as dispersed phase on their morphology and tensile properties was studied. Polymers grafted with maleic anhydride were used as compatibilizer agents. The blends were prepared via melt blending in an internal mixer at 200°C and characterized in terms of solution viscometry of the PLA phase, infrared spectroscopy, and scanning and transmission electron microscopy. Results showed that the processing of PLA produced thermo-mechanical degradation in the polymer and a significant decrease in the viscosity molecular weight of the PLA phase in the different composites. The large sizes of the dispersed phases in the unfilled PLA blends and the low values of the tensile properties could be attributed to the thermo-mechanical degradation of the PLA matrix during its processing. The blends with PLA as matrix a...
Revista Latinoamericana de Metalurgia y Materiales, Jun 1, 2014
In the present work, the influence of degradation during the processing in the tensile properties... more In the present work, the influence of degradation during the processing in the tensile properties of blends of poly (lactic acid), montmorillonite and two types of polyolefins as dispersed phases was studied. Polymers grafted with maleic anhydride were employed as the compatibilizing agents. The nanocomposites and their blends were prepared in an internal mixer at 200°C and characterized using solution viscometry of the PLA phase, infrared spectroscopy (FTIR) and transmission and scanning electron microscopy (TEM and SEM). The melt processing of the PLA produced its thermo-mechanical degradation and a steep decrease in its molecular weight. The large size of the dispersed phases in the PLA and the poor tensile properties of the blends without clay were attributed to the thermal degradation of the PLA matrix during their processing. Changes in the molecular weight of the PLA in blends without montmorillonite depend on the type of disperse phase and on the efficiency as emulsifier of the compatibilizing agent employed. The presence of montmorillonite slightly increased the Young's modulus values of the blends. Smaller particle sizes of the dispersed phase were found in blends with the clay; however, optimal tensile properties were not found.
Revista Colombiana de Hematología y Oncología, Sep 1, 2012
Se prepararon compuestos de poli (ácido láctico) con almidón de maíz en una extrusora doble torni... more Se prepararon compuestos de poli (ácido láctico) con almidón de maíz en una extrusora doble tornillo. Se estudió la influencia de incorporar diferentes proporciones de carga en las propiedades y para ello se emplearon las técnicas de viscosimetría en solución, reometría dinámica en flujo oscilatorio, análisis termo-gravimétrico (TGA) y microscopía electrónica de barrido. También se determinaron las propiedades de tracción. Se estableció que la cinética de degradación termo-oxidativa del PLA y de las correspondientes fases de PLA en los compuestos con almidón de maíz bajo condiciones isotérmicas en el reómetro dinámico es por escisión de cadenas al azar. También se encontró que la degradación térmica e hidrolítica durante el procesado de la fase PLA en los compuestos se ajustó al modelo que considera el efecto catalítico de los grupos de ácidos carboxílicos terminales en esta fase. Además, se utilizaron varios modelos para predecir las relaciones de viscosidad a frecuencia y temperatura constantes, relaciones de esfuerzos y elongaciones a la ruptura para estos compuestos y el mejor ajuste con los valores experimentales se obtiene con los modelos de Maron-Pierce y de Thomas, Nicolais y Narkis y Nielsen, respectivamente. Los resultados mostraron que los compuestos con almidón de maíz poseen una mayor susceptibilidad a la degradación termo-mecánica e hidrolítica en el procesado que el PLA solamente inyectado, debido a la mayor adsorción de humedad del almidón en la alimentación a la extrusora. Esta mayor degradación durante el procesado le confiere a estos materiales similares valores de esfuerzos y módulos de elasticidad que aquellos del PLA inyectado debido a la cristalinidad inducida por la mayor movilidad molecular. Sin embargo, la viscosidad y módulo de almacenamiento a bajas frecuencias, elongación a la ruptura y estabilidad tanto a la degradación térmica en atmósfera inerte (TGA) como termo-oxidativa en el reómetro bajo condiciones isotérmicas son menores.
Poly (lactic acid) (PLA) composites with corn starch were prepared in a corotating twin-screw ext... more Poly (lactic acid) (PLA) composites with corn starch were prepared in a corotating twin-screw extruder. The influence of incorporating different proportions of filler was studied in terms of intrinsic viscosities, oscillatory shear flow, thermogravimetric analysis (TGA), scanning electron microscopy and tensile properties. Results showed that the kinetics of the thermo-oxidative reaction of the PLA and also of the PLA phase in the composites with corn starch under isothermal conditions in the dynamic rheometer was mainly a random chain splitting process. The thermal and hydrolytic degradation of the PLA phase in the composites with corn starch during their processing were fitted in an autocatalyzed carboxylic group degradation model. Also, several models were employed to predict the viscosity ratio at constant frequency and temperature, the tensile strength and elongation at break ratios and it was found that the experimental values in the composites lie close to those of the Maron-...
Revista de la Facultad de Ingeniería Universidad Central de Venezuela, Mar 10, 2013
En este trabajo se estudió la compatibilidad en mezclas de Poliamida-6 (PA) y diferent... more En este trabajo se estudió la compatibilidad en mezclas de Poliamida-6 (PA) y diferentes polietilenos: polietileno de altadensidad (PEAD), polietileno de baja densidad (PEBD) y polietileno lineal de baja densidad (PELBD). Se utilizó un copolímeroestireno-etileno/butileno-estireno funcionalizado con dietil maleato como agente compatibilizante (SEBS-f-DEM). Lacaracterización de las mezclas se llevó a cabo utilizando las técnicas de Calorimetría Diferencial de Barrido (DSC),Espectroscopía Infrarroja de Transformada de Fourier (FTIR), Microscopía Electrónica de Barrido (SEM) y la determinaciónde las propiedades de impacto Izod con entalla. Los ensayos de extracción selectiva realizados permitieron inferir laprobable existencia de interacciones entre los grupos de la PA y del SEBS-f-DEM. Por medio de DSC se evidenció elfenómeno de cristalización fraccionada de la PA sólo en las mezclas compatibilizadas cuya fase dispersa es la PA. Engeneral, se obtuvo un mejoramiento de las propiedades de impacto de la PA en las mezclas reactivas en las que se utilizóPELBD como matriz. Mediante el análisis por SEM de las superficies de fractura de las mezclas, se pudo evidenciar que laincorporación del SEBS-f-DEM como agente compatibilizante produce una disminución significativa en el tamaño departículas de la fase dispersa.Palabras clave: Poliamida, Polietileno, Mezclas reactivas, Extrusión reactiva, Funcionalización.ABSTRACTIn this work, the compatibility in blends of Polyamide 6 (PA) and three different Polyethylenes, High-Density (HDPE), Low-Density (LDPE) and Linear Low-Density (LLDPE) polyethylenes, was studied. A copolymer of styrene/ethylene-butylene/styrene functionalized with diethyl maleate (SEBS-g-DEM) was used as compatibilizing agent. The characterization of theblends was carried out using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR),Scanning Electron Microscopy (SEM) and through notched-Izod impact tests. Results from selective extraction testsdisplayed that interactions between PA and SEBS-g-DEM groups are likely present. Through DSC results, the fractionatedcrystallization phenomenon of the PA was unfolded, only in those blends where the PA was the dispersed phase. Ingeneral, an enhancement in the impact resistance of those reactive blends where LLDPE was used as the matrix wasobtained. SEM analyses of the fractured surfaces of the blends showed that the incorporation of SEBS-g-DEM ascompatibilizing agent produced a significant decrease in the particle size of the dispersed phase.Keywords: Polyamide, Polyethylene, Reactive blends, Reactive extrusion, Functionalization
In this work, the compatibility in blends of Polyamide 6 (PA) and three different Polyethylenes, ... more In this work, the compatibility in blends of Polyamide 6 (PA) and three different Polyethylenes, High-Density (HDPE), LowDensity (LDPE) and Linear Low-Density (LLDPE) polyethylenes, was studied. A copolymer of styrene/ethylene-butylene/ styrene functionalized with diethyl maleate (SEBS-g-DEM) was used as compatibilizing agent. The characterization of the blends was carried out using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and through notched-Izod impact tests. Results from selective extraction tests displayed that interactions between PA and SEBS-g-DEM groups are likely present. Through DSC results, the fractionated crystallization phenomenon of the PA was unfolded, only in those blends where the PA was the dispersed phase. In general, an enhancement in the impact resistance of those reactive blends where LLDPE was used as the matrix was obtained. SEM analyses of the fractured surfaces of the blends ...
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
En esta investigación se realizaron mezclas de dos tipos comerciales de policloruro de vinilo con... more En esta investigación se realizaron mezclas de dos tipos comerciales de policloruro de vinilo con polietilenos lineales de baja densidad (PELBD) y polietilenos de alta densidad (PEAD) puros y funcionalizados. Para la funcionalización de los polietilenos se emplearon diferentes proporciones de iniciador (dicumilperóxido) y 10 ppc de agente funcionalizante (dietilmaleato). Las mezclas fueron preparadas en una extrusora de doble tornillo en una proporción PVC/PE de 65/35. El grado de funcionalización de los polietilenos fue determinado por espectroscopia infrarroja por transformada de Fourier (FTIR). Las mezclas fueron caracterizadas mediante calorimetría diferencial de barrido (DSC) y propiedades mecánicas de tracción e impacto y su morfología fue determinada mediante microscopía electrónica de barrido (MEB). La funcionalización de los polietilenos mejoró la procesabilidad de las mezclas de éstos con el PVC. En las mezclas preparadas con el PVC de menor valor K y con el PELBD de más b...
Revista de Chimie, 2022
Nanocomposites of poly(lactic acid) with sepiolite needles (5 wt.%) were evaluated in terms of th... more Nanocomposites of poly(lactic acid) with sepiolite needles (5 wt.%) were evaluated in terms of the mechanical and biofilm formation properties. The nanocomposite exhibited higher values of the Young�s modulus and tensile strength at break compared to the PLA, without detriment in the percent elongation at break. These improvements were related to the high aspect ratio of the nanoclay, the polymer-clay interactions, and the degree of dispersion. The growth of Pseudomonas aeruginosa on the surface of the PLA and nPLA materials was promoted in different conditions. Medium with different concentration of nutrients were used and also were compared the effect of the medium physical state (solid or liquid medium). Biofilms were formed in all the conditions. However, the nanocomposite presented a higher area coverage of microorganisms on its surface, possibly due to the positive effects of the nanoclay on the bacterial adhesion.
Latin American Applied Research, 1996
Grafting of Poltethylenes
Preface Introduction Techniques Used to Prepare Grafted Polythylenes Secondary &/Or Degradation R... more Preface Introduction Techniques Used to Prepare Grafted Polythylenes Secondary &/Or Degradation Reactions in the Grafting Process Molecular Weight Distribution & Rheological Properties Thermal Properties & Thermogravimetric Analysis (TGA) Conclusion Index.
Revista de la Facultad de Ingenieria
In this work, the rheological, morphological and mechanical behaviors of nanocomposites based on ... more In this work, the rheological, morphological and mechanical behaviors of nanocomposites based on blends of polypropylene and metallocene polyethylene (mPE), reinforced with organically modified montmorillonite and prepared through melt blending, are studied. Two different compatibilizing agents were employed: a PP grafted with maleic anhydride (AM) commercially available, and a PP grafted with the same monomer in our laboratory. The grafting degrees of both compatibilizers were determined through Fourier transformed infrared spectroscopy (FTIR). Additionally, the rheological properties in dynamic shear and the mechanical properties in tension of the composites were studied. The morphologies of the nanoparticles and of the dispersed phase were characterized using TEM and SEM microscopy, respectively. The compatibilizing agent prepared in our laboratory has a higher grafting degree than that of the commercial one. The dynamic rheological properties of the nanocomposites are higher tha...
Polymer Degradation and Stability, 2012
The thermal properties and the kinetics of thermal degradation of nanocomposites of polypropylene... more The thermal properties and the kinetics of thermal degradation of nanocomposites of polypropylene (PP) and montmorillonite (OMMT) and an ethylene-co-vinyl acetate copolymer (EVA) as a minority phase, including a third elastomeric component represented by poly(ethylene-co-octene) (mPE) were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two maleic anhydride modified PP (PP-g-AM), one of them commercial and the other one prepared in our laboratory, were used as compatibilizers. The expected nucleating effect of the organoclay in the nanocomposites and the increase on crystallization temperature was observed. The degradation kinetic parameters were obtained using the Coats e Redfern integral method to obtain the reaction order and the E 2 function methodology to calculate the activation energy. The PP/OMMT nanocomposites with mPE or EVA exhibited higher degradation temperatures and activation energies than the neat PP and also a higher decomposition temperature than the PP nanocomposites without the elastomeric minority phase. The employment of the commercial compatibilizer generated more exfoliated structures on the ternary nanocomposites that contributed to a better thermal stability. The degradation mechanisms involve crosslinking, chain branching and chain scission reactions for the ternary PP/OMMT/mPE nanocomposites and an additional accelerated deacetylation process for the ternary PP/OMMT/EVA nanocomposites.
Advanced Materials Research, 2008
The need for solid-waste management has pushed the development of alternative systems for recycli... more The need for solid-waste management has pushed the development of alternative systems for recycling and revalue used plastic containers. Poly(ethylene terephthalate) (PET) is being widely used as raw material for beverage bottles. However, as has been widely reported, PET undergoes degradation and hydrolysis when reprocessed. On the other hand, poly(butylene terephthalate) (PBT) is another thermoplastic polyester with easy processability but high brittleness and cost. Hence, it has been blended with other polymers such as polypropylene to overcome its disadvantages. In this work, bentonite was incorporated into recycled PET and PBT/polypropylene blends by extrusion. Rheological and tensile properties and processability of the composites thus prepared were studied. Results showed a strong newtonean character of extrudates of recycled PET and higher viscosities and a more pseudoplastic behavior and improved reprocessability when bentonite was added to PET. Furthermore, inclusion of th...
Advanced Materials Research, 2008
Polypropylene/polyamide-6 and polypropylene/metallocene polyethylene blends containing 2.5 phr of... more Polypropylene/polyamide-6 and polypropylene/metallocene polyethylene blends containing 2.5 phr of organophilic modified montmorillonite were prepared in a twin-screw extruder followed by injection molding. In order to compare, blends without layered clay were also made. Styreneethylene- butylene-styrene copolymer and polypropylene grafted with anhydride maleic were used as compatibilizers in the ternary blends and in the PP nanocomposite preparation, respectively. The presence of tactoids, intercalated and exfoliated structures was observed by TEM in some of the samples containing layered clay and modified PP materials. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant changes in tensile moduli were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene exhibited better tensile toughness and lower tensile mo...
Polymer Composites, 2006
ABSTRACT The preparation of polypropylene (PP) nanocomposites was studied using clay and three ty... more ABSTRACT The preparation of polypropylene (PP) nanocomposites was studied using clay and three types of modified PP (m-PP) as compatibilizers: diethyl maleate grafted PP (PP-g-DEM), maleic anhydride grafted PP (PP-g-MA), and PP grafted with carbamyl maleamic acid (PP-g-UMA). The clay was made organophylic by an acid treatment with octadecylamine. PP functionalization and blending were carried out in an internal mixer. Blends of PP containing 20 and 40 wt% each of the modified PP and 5 wt% of organophilic clay (IMt), in each case, were prepared. Samples were characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), optical microscopy, and mechanical testing. The presence of tactoid, intercalated and exfoliated structures was observed by TEM in all the samples containing clay and modified PP, which also showed improved mechanical properties with tensile modulus as much as three times that of PP. Melting temperature did not vary significantly with the addition of clay. However, because of the clay's nucleating effect, an increase in the crystallization temperature was observed, accompanied by a slight decrease in the degree of crystallinity. The best results were obtained when PP-g-MA was used as the compatibilizer; intermediate results were obtained with the use of PP-g-UMA, followed by the results obtained when PP-g-DEM was used. Property enhancements were obtained when a higher percentage of modified PP was employed. POLYM. COMPOS., 27:451–460, 2006. © 2006 Society of Plastics Engineers
Journal of Macromolecular Science, Part A, 1998
The viscoelastic and morphological properties of ternary reactive blends of different low and lin... more The viscoelastic and morphological properties of ternary reactive blends of different low and linear low density polyethylenes, polyamide-6 and functionalized SEBS were studied. The SEBS was functionalized via reactive extrusion using diethylmaleate as the functionalizing monomer. Even though the grafting degree achieved was very low (about 0.040 wt%) due to the high melt viscosity of the SEBS, a lower particle
Rev. LatinAm. Met. …, 2006
This work is a brief compilation of our results from previous researches concerning the influence... more This work is a brief compilation of our results from previous researches concerning the influence of the rheological parameters on polyolefin blends, reactive blends, polymer grafting, polypropylene nanocomposites, polyamide nanocomposites (PA) and its blends. ...
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, Dec 1, 2017
Revista Tecnica De La Facultad De Ingenieria Universidad Del Zulia, 2017
La acumulacion de virutas de polietileno de ultra alto peso molecular (PEUAPM), producto del meca... more La acumulacion de virutas de polietileno de ultra alto peso molecular (PEUAPM), producto del mecanizado de elementos de maquina, genera diversos problemas en las plantas de produccion. Con el objeto de plantear una posible reutilizacion de estos residuos y reducir su impacto sobre el ambiente, se prepararon mezclas con base en diferentes proporciones de este material y dos polietilenos de alta densidad (PEAD): grado extrusion y grado inyeccion. Se evaluaron las propiedades reologicas y mecanicas (traccion y abrasion) de las mezclas preparadas y se observo su morfologia mediante microscopia electronica de barrido. Todas las mezclas fueron procesadas en una extrusora de doble tornillo y se moldearon placas por compresion. Cuando se compararon los diferentes productos con los PEAD puros, todos exhibieron un aumento en la resistencia a la abrasion, se obtuvieron pocas variaciones en las propiedades en traccion y se encontro un aumento de las viscosidades complejas y de los modulos de almacenamiento y de perdidas con el contenido de PEUAPM. Ademas, es de resaltar que se logro preparar un nuevo material (PEAD grado inyeccion/PEUAPM, 80/20) con propiedades de traccion y comportamiento reologico semejantes al PEAD grado extrusion, que podria sustituir a este ultimo en aplicaciones similares
In the present work, the influence of the degradation during the processing of nanocomposites of ... more In the present work, the influence of the degradation during the processing of nanocomposites of poly (lactic acid) (PLA) with montmorillonite and its blends with low density polyethylene as dispersed phase on their morphology and tensile properties was studied. Polymers grafted with maleic anhydride were used as compatibilizer agents. The blends were prepared via melt blending in an internal mixer at 200°C and characterized in terms of solution viscometry of the PLA phase, infrared spectroscopy, and scanning and transmission electron microscopy. Results showed that the processing of PLA produced thermo-mechanical degradation in the polymer and a significant decrease in the viscosity molecular weight of the PLA phase in the different composites. The large sizes of the dispersed phases in the unfilled PLA blends and the low values of the tensile properties could be attributed to the thermo-mechanical degradation of the PLA matrix during its processing. The blends with PLA as matrix a...
Revista Latinoamericana de Metalurgia y Materiales, Jun 1, 2014
In the present work, the influence of degradation during the processing in the tensile properties... more In the present work, the influence of degradation during the processing in the tensile properties of blends of poly (lactic acid), montmorillonite and two types of polyolefins as dispersed phases was studied. Polymers grafted with maleic anhydride were employed as the compatibilizing agents. The nanocomposites and their blends were prepared in an internal mixer at 200°C and characterized using solution viscometry of the PLA phase, infrared spectroscopy (FTIR) and transmission and scanning electron microscopy (TEM and SEM). The melt processing of the PLA produced its thermo-mechanical degradation and a steep decrease in its molecular weight. The large size of the dispersed phases in the PLA and the poor tensile properties of the blends without clay were attributed to the thermal degradation of the PLA matrix during their processing. Changes in the molecular weight of the PLA in blends without montmorillonite depend on the type of disperse phase and on the efficiency as emulsifier of the compatibilizing agent employed. The presence of montmorillonite slightly increased the Young's modulus values of the blends. Smaller particle sizes of the dispersed phase were found in blends with the clay; however, optimal tensile properties were not found.
Revista Colombiana de Hematología y Oncología, Sep 1, 2012
Se prepararon compuestos de poli (ácido láctico) con almidón de maíz en una extrusora doble torni... more Se prepararon compuestos de poli (ácido láctico) con almidón de maíz en una extrusora doble tornillo. Se estudió la influencia de incorporar diferentes proporciones de carga en las propiedades y para ello se emplearon las técnicas de viscosimetría en solución, reometría dinámica en flujo oscilatorio, análisis termo-gravimétrico (TGA) y microscopía electrónica de barrido. También se determinaron las propiedades de tracción. Se estableció que la cinética de degradación termo-oxidativa del PLA y de las correspondientes fases de PLA en los compuestos con almidón de maíz bajo condiciones isotérmicas en el reómetro dinámico es por escisión de cadenas al azar. También se encontró que la degradación térmica e hidrolítica durante el procesado de la fase PLA en los compuestos se ajustó al modelo que considera el efecto catalítico de los grupos de ácidos carboxílicos terminales en esta fase. Además, se utilizaron varios modelos para predecir las relaciones de viscosidad a frecuencia y temperatura constantes, relaciones de esfuerzos y elongaciones a la ruptura para estos compuestos y el mejor ajuste con los valores experimentales se obtiene con los modelos de Maron-Pierce y de Thomas, Nicolais y Narkis y Nielsen, respectivamente. Los resultados mostraron que los compuestos con almidón de maíz poseen una mayor susceptibilidad a la degradación termo-mecánica e hidrolítica en el procesado que el PLA solamente inyectado, debido a la mayor adsorción de humedad del almidón en la alimentación a la extrusora. Esta mayor degradación durante el procesado le confiere a estos materiales similares valores de esfuerzos y módulos de elasticidad que aquellos del PLA inyectado debido a la cristalinidad inducida por la mayor movilidad molecular. Sin embargo, la viscosidad y módulo de almacenamiento a bajas frecuencias, elongación a la ruptura y estabilidad tanto a la degradación térmica en atmósfera inerte (TGA) como termo-oxidativa en el reómetro bajo condiciones isotérmicas son menores.
Poly (lactic acid) (PLA) composites with corn starch were prepared in a corotating twin-screw ext... more Poly (lactic acid) (PLA) composites with corn starch were prepared in a corotating twin-screw extruder. The influence of incorporating different proportions of filler was studied in terms of intrinsic viscosities, oscillatory shear flow, thermogravimetric analysis (TGA), scanning electron microscopy and tensile properties. Results showed that the kinetics of the thermo-oxidative reaction of the PLA and also of the PLA phase in the composites with corn starch under isothermal conditions in the dynamic rheometer was mainly a random chain splitting process. The thermal and hydrolytic degradation of the PLA phase in the composites with corn starch during their processing were fitted in an autocatalyzed carboxylic group degradation model. Also, several models were employed to predict the viscosity ratio at constant frequency and temperature, the tensile strength and elongation at break ratios and it was found that the experimental values in the composites lie close to those of the Maron-...
Revista de la Facultad de Ingeniería Universidad Central de Venezuela, Mar 10, 2013
En este trabajo se estudió la compatibilidad en mezclas de Poliamida-6 (PA) y diferent... more En este trabajo se estudió la compatibilidad en mezclas de Poliamida-6 (PA) y diferentes polietilenos: polietileno de altadensidad (PEAD), polietileno de baja densidad (PEBD) y polietileno lineal de baja densidad (PELBD). Se utilizó un copolímeroestireno-etileno/butileno-estireno funcionalizado con dietil maleato como agente compatibilizante (SEBS-f-DEM). Lacaracterización de las mezclas se llevó a cabo utilizando las técnicas de Calorimetría Diferencial de Barrido (DSC),Espectroscopía Infrarroja de Transformada de Fourier (FTIR), Microscopía Electrónica de Barrido (SEM) y la determinaciónde las propiedades de impacto Izod con entalla. Los ensayos de extracción selectiva realizados permitieron inferir laprobable existencia de interacciones entre los grupos de la PA y del SEBS-f-DEM. Por medio de DSC se evidenció elfenómeno de cristalización fraccionada de la PA sólo en las mezclas compatibilizadas cuya fase dispersa es la PA. Engeneral, se obtuvo un mejoramiento de las propiedades de impacto de la PA en las mezclas reactivas en las que se utilizóPELBD como matriz. Mediante el análisis por SEM de las superficies de fractura de las mezclas, se pudo evidenciar que laincorporación del SEBS-f-DEM como agente compatibilizante produce una disminución significativa en el tamaño departículas de la fase dispersa.Palabras clave: Poliamida, Polietileno, Mezclas reactivas, Extrusión reactiva, Funcionalización.ABSTRACTIn this work, the compatibility in blends of Polyamide 6 (PA) and three different Polyethylenes, High-Density (HDPE), Low-Density (LDPE) and Linear Low-Density (LLDPE) polyethylenes, was studied. A copolymer of styrene/ethylene-butylene/styrene functionalized with diethyl maleate (SEBS-g-DEM) was used as compatibilizing agent. The characterization of theblends was carried out using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR),Scanning Electron Microscopy (SEM) and through notched-Izod impact tests. Results from selective extraction testsdisplayed that interactions between PA and SEBS-g-DEM groups are likely present. Through DSC results, the fractionatedcrystallization phenomenon of the PA was unfolded, only in those blends where the PA was the dispersed phase. Ingeneral, an enhancement in the impact resistance of those reactive blends where LLDPE was used as the matrix wasobtained. SEM analyses of the fractured surfaces of the blends showed that the incorporation of SEBS-g-DEM ascompatibilizing agent produced a significant decrease in the particle size of the dispersed phase.Keywords: Polyamide, Polyethylene, Reactive blends, Reactive extrusion, Functionalization
In this work, the compatibility in blends of Polyamide 6 (PA) and three different Polyethylenes, ... more In this work, the compatibility in blends of Polyamide 6 (PA) and three different Polyethylenes, High-Density (HDPE), LowDensity (LDPE) and Linear Low-Density (LLDPE) polyethylenes, was studied. A copolymer of styrene/ethylene-butylene/ styrene functionalized with diethyl maleate (SEBS-g-DEM) was used as compatibilizing agent. The characterization of the blends was carried out using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and through notched-Izod impact tests. Results from selective extraction tests displayed that interactions between PA and SEBS-g-DEM groups are likely present. Through DSC results, the fractionated crystallization phenomenon of the PA was unfolded, only in those blends where the PA was the dispersed phase. In general, an enhancement in the impact resistance of those reactive blends where LLDPE was used as the matrix was obtained. SEM analyses of the fractured surfaces of the blends ...
Revista Técnica de la Facultad de Ingeniería Universidad del Zulia
En esta investigación se realizaron mezclas de dos tipos comerciales de policloruro de vinilo con... more En esta investigación se realizaron mezclas de dos tipos comerciales de policloruro de vinilo con polietilenos lineales de baja densidad (PELBD) y polietilenos de alta densidad (PEAD) puros y funcionalizados. Para la funcionalización de los polietilenos se emplearon diferentes proporciones de iniciador (dicumilperóxido) y 10 ppc de agente funcionalizante (dietilmaleato). Las mezclas fueron preparadas en una extrusora de doble tornillo en una proporción PVC/PE de 65/35. El grado de funcionalización de los polietilenos fue determinado por espectroscopia infrarroja por transformada de Fourier (FTIR). Las mezclas fueron caracterizadas mediante calorimetría diferencial de barrido (DSC) y propiedades mecánicas de tracción e impacto y su morfología fue determinada mediante microscopía electrónica de barrido (MEB). La funcionalización de los polietilenos mejoró la procesabilidad de las mezclas de éstos con el PVC. En las mezclas preparadas con el PVC de menor valor K y con el PELBD de más b...
Revista de Chimie, 2022
Nanocomposites of poly(lactic acid) with sepiolite needles (5 wt.%) were evaluated in terms of th... more Nanocomposites of poly(lactic acid) with sepiolite needles (5 wt.%) were evaluated in terms of the mechanical and biofilm formation properties. The nanocomposite exhibited higher values of the Young�s modulus and tensile strength at break compared to the PLA, without detriment in the percent elongation at break. These improvements were related to the high aspect ratio of the nanoclay, the polymer-clay interactions, and the degree of dispersion. The growth of Pseudomonas aeruginosa on the surface of the PLA and nPLA materials was promoted in different conditions. Medium with different concentration of nutrients were used and also were compared the effect of the medium physical state (solid or liquid medium). Biofilms were formed in all the conditions. However, the nanocomposite presented a higher area coverage of microorganisms on its surface, possibly due to the positive effects of the nanoclay on the bacterial adhesion.
Latin American Applied Research, 1996
Grafting of Poltethylenes
Preface Introduction Techniques Used to Prepare Grafted Polythylenes Secondary &/Or Degradation R... more Preface Introduction Techniques Used to Prepare Grafted Polythylenes Secondary &/Or Degradation Reactions in the Grafting Process Molecular Weight Distribution & Rheological Properties Thermal Properties & Thermogravimetric Analysis (TGA) Conclusion Index.
Revista de la Facultad de Ingenieria
In this work, the rheological, morphological and mechanical behaviors of nanocomposites based on ... more In this work, the rheological, morphological and mechanical behaviors of nanocomposites based on blends of polypropylene and metallocene polyethylene (mPE), reinforced with organically modified montmorillonite and prepared through melt blending, are studied. Two different compatibilizing agents were employed: a PP grafted with maleic anhydride (AM) commercially available, and a PP grafted with the same monomer in our laboratory. The grafting degrees of both compatibilizers were determined through Fourier transformed infrared spectroscopy (FTIR). Additionally, the rheological properties in dynamic shear and the mechanical properties in tension of the composites were studied. The morphologies of the nanoparticles and of the dispersed phase were characterized using TEM and SEM microscopy, respectively. The compatibilizing agent prepared in our laboratory has a higher grafting degree than that of the commercial one. The dynamic rheological properties of the nanocomposites are higher tha...
Polymer Degradation and Stability, 2012
The thermal properties and the kinetics of thermal degradation of nanocomposites of polypropylene... more The thermal properties and the kinetics of thermal degradation of nanocomposites of polypropylene (PP) and montmorillonite (OMMT) and an ethylene-co-vinyl acetate copolymer (EVA) as a minority phase, including a third elastomeric component represented by poly(ethylene-co-octene) (mPE) were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Two maleic anhydride modified PP (PP-g-AM), one of them commercial and the other one prepared in our laboratory, were used as compatibilizers. The expected nucleating effect of the organoclay in the nanocomposites and the increase on crystallization temperature was observed. The degradation kinetic parameters were obtained using the Coats e Redfern integral method to obtain the reaction order and the E 2 function methodology to calculate the activation energy. The PP/OMMT nanocomposites with mPE or EVA exhibited higher degradation temperatures and activation energies than the neat PP and also a higher decomposition temperature than the PP nanocomposites without the elastomeric minority phase. The employment of the commercial compatibilizer generated more exfoliated structures on the ternary nanocomposites that contributed to a better thermal stability. The degradation mechanisms involve crosslinking, chain branching and chain scission reactions for the ternary PP/OMMT/mPE nanocomposites and an additional accelerated deacetylation process for the ternary PP/OMMT/EVA nanocomposites.
Advanced Materials Research, 2008
The need for solid-waste management has pushed the development of alternative systems for recycli... more The need for solid-waste management has pushed the development of alternative systems for recycling and revalue used plastic containers. Poly(ethylene terephthalate) (PET) is being widely used as raw material for beverage bottles. However, as has been widely reported, PET undergoes degradation and hydrolysis when reprocessed. On the other hand, poly(butylene terephthalate) (PBT) is another thermoplastic polyester with easy processability but high brittleness and cost. Hence, it has been blended with other polymers such as polypropylene to overcome its disadvantages. In this work, bentonite was incorporated into recycled PET and PBT/polypropylene blends by extrusion. Rheological and tensile properties and processability of the composites thus prepared were studied. Results showed a strong newtonean character of extrudates of recycled PET and higher viscosities and a more pseudoplastic behavior and improved reprocessability when bentonite was added to PET. Furthermore, inclusion of th...
Advanced Materials Research, 2008
Polypropylene/polyamide-6 and polypropylene/metallocene polyethylene blends containing 2.5 phr of... more Polypropylene/polyamide-6 and polypropylene/metallocene polyethylene blends containing 2.5 phr of organophilic modified montmorillonite were prepared in a twin-screw extruder followed by injection molding. In order to compare, blends without layered clay were also made. Styreneethylene- butylene-styrene copolymer and polypropylene grafted with anhydride maleic were used as compatibilizers in the ternary blends and in the PP nanocomposite preparation, respectively. The presence of tactoids, intercalated and exfoliated structures was observed by TEM in some of the samples containing layered clay and modified PP materials. Results showed that the compatibilized blends prepared without clay are tougher than those prepared with the nanocomposite of PP as the matrix phase and no significant changes in tensile moduli were observed between them. However, the binary blend with a nanocomposite of PP as matrix and metallocene polyethylene exhibited better tensile toughness and lower tensile mo...
Polymer Composites, 2006
ABSTRACT The preparation of polypropylene (PP) nanocomposites was studied using clay and three ty... more ABSTRACT The preparation of polypropylene (PP) nanocomposites was studied using clay and three types of modified PP (m-PP) as compatibilizers: diethyl maleate grafted PP (PP-g-DEM), maleic anhydride grafted PP (PP-g-MA), and PP grafted with carbamyl maleamic acid (PP-g-UMA). The clay was made organophylic by an acid treatment with octadecylamine. PP functionalization and blending were carried out in an internal mixer. Blends of PP containing 20 and 40 wt% each of the modified PP and 5 wt% of organophilic clay (IMt), in each case, were prepared. Samples were characterized by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), optical microscopy, and mechanical testing. The presence of tactoid, intercalated and exfoliated structures was observed by TEM in all the samples containing clay and modified PP, which also showed improved mechanical properties with tensile modulus as much as three times that of PP. Melting temperature did not vary significantly with the addition of clay. However, because of the clay's nucleating effect, an increase in the crystallization temperature was observed, accompanied by a slight decrease in the degree of crystallinity. The best results were obtained when PP-g-MA was used as the compatibilizer; intermediate results were obtained with the use of PP-g-UMA, followed by the results obtained when PP-g-DEM was used. Property enhancements were obtained when a higher percentage of modified PP was employed. POLYM. COMPOS., 27:451–460, 2006. © 2006 Society of Plastics Engineers
Journal of Macromolecular Science, Part A, 1998
The viscoelastic and morphological properties of ternary reactive blends of different low and lin... more The viscoelastic and morphological properties of ternary reactive blends of different low and linear low density polyethylenes, polyamide-6 and functionalized SEBS were studied. The SEBS was functionalized via reactive extrusion using diethylmaleate as the functionalizing monomer. Even though the grafting degree achieved was very low (about 0.040 wt%) due to the high melt viscosity of the SEBS, a lower particle
Rev. LatinAm. Met. …, 2006
This work is a brief compilation of our results from previous researches concerning the influence... more This work is a brief compilation of our results from previous researches concerning the influence of the rheological parameters on polyolefin blends, reactive blends, polymer grafting, polypropylene nanocomposites, polyamide nanocomposites (PA) and its blends. ...
When polyolefins are functionalized to modify its chemical structure and polarity, some other sec... more When polyolefins are functionalized to modify its chemical structure and polarity, some other secondary reactions take place as well. The grafting of a different monomer onto the main chain of the polymer involves the use of a free radical initiator, such as a peroxide, or irradiation of the sample (gamma rays or ultrasound), that not only provide the free radicals for the grafting but also for main chain modifications. Different reaction processes such as functionalization in solution, reactive extrusion or irradiation produce different structures. This new book deals with modifications of the main chain as a consequence of polyolefin grafting through different techniques, such as functionalization in solution and reactive extrusion and through polymer irradiation with gamma rays and ultrasound.